1. Field of the Invention
This invention relates to a misalignment measuring method, in which when an object, such as a mask, is aligned with another object, such as a wafer, and patterns on the object are printed on the other object using, for example, an exposure apparatus for manufacturing semiconductor devices, the accuracy of the alignment is measured. The invention also relates to a position detection apparatus which uses such a method.
2. Description of the Related Art
In a so-called exposure transfer apparatus (an exposure apparatus) for manufacturing semiconductor devices which exposes and transfers a circuit pattern formed on a reticle onto a photosensitive material coated on a wafer using ultraviolet rays, X-rays, or the like, relative alignment between the reticle (a first object) and the wafer (a second object) is an important factor for improving the performance of obtained semiconductor devices. Particularly in alignment in recent exposure apparatuses, for example, an accuracy in alignment of less than a micrometer is required in order to realize high-integration semiconductor devices.
In many alignment apparatuses, so-called alignment patterns are provided on the surfaces of a reticle and a wafer, and the wafer is aligned with the reticle utilizing information relating to the positions of the alignment patterns. Conventionally, in order to actually measure and evaluate the alignment performance of an apparatus provided as an exposure apparatus, two fine patterns formed on a reticle are aligned with and printed on a wafer, and the amount of deviation between the two patterns on the wafer is obtained by performing visual measurement, image processing, or the like.
When measuring the amount of deviation between patterns on a wafer in such an alignment apparatus, for example, the following problems arise in visual measurement.
(1) Accuracy in the measurement is unstable, because the measurement greatly depends on the experience and skill of a person who performs the visual measurement.
(2) Time and much manual effort are needed because of non-automatic measurement.
(3) High accuracy in the measurement cannot obtained.
Also in measurement performed by image processing, problems arise in that, for example, time is needed because the processing is complicated, and high accuracy in the measurement cannot be obtained.